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JordyUSAandClaude Opus 5.5
2f4b59329e
New L0 crate written from the AVI RIFF file reference and OpenDML 1.02: avih and per-stream strh / strf (BITMAPINFOHEADER, WAVEFORMATEX(TENSIBLE)) / strn, and chunk tables from the best index a file has: the OpenDML indx super index and ix## standard indexes (field indexes too), else idx1 (offsets relative to movi or absolute) plus a scan of RIFF AVIX extensions it cannot see, else a scan of the movi lists (key frames then unknown). Frames are read on demand through a ByteSource. Sizes are clamped to the file, so a cut-off recording opens with what is there; rec lists nest at most 3 deep and tables are bounded by what the file could hold. Tests: hand-built files for every index path, truncation, and every single-byte mutation and truncation (no panic); ffmpeg-made files against ffprobe; an ignored test on a 1.16 GB OpenDML file with AVIX extensions. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
44 lines
2.2 KiB
Markdown
44 lines
2.2 KiB
Markdown
# filmcraft-avi
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A clean-room AVI demuxer, written from Microsoft's published AVI RIFF file reference and the
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OpenDML AVI File Format Extensions 1.02. Layer L0: no dependencies beyond `std`, no `unsafe`, builds
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for `wasm32-unknown-unknown`. No FFmpeg, libavformat or other AVI implementation was read; ffmpeg
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and ffprobe are used only as external **test oracles**.
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## API
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```rust
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use filmcraft_avi::{open, StreamKind};
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let file = open(&bytes)?; // any ByteSource: a slice, a file, a web Blob…
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for (i, s) in file.streams.iter().enumerate() {
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match s.kind {
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StreamKind::Video => println!("{:?} {} fps", s.video.as_ref().map(|b| b.compression), s.rate as f64 / s.scale as f64),
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StreamKind::Audio => println!("format 0x{:04x}", s.audio.as_ref().map_or(0, |w| w.format_tag)),
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_ => {}
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}
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let first = file.read_chunk(&bytes, i, 0)?; // frame data, on demand
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}
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```
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## What it reads
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| Part | |
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|---|---|
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| Headers | `avih`; per stream `strh`, `strf` (`BITMAPINFOHEADER`, `WAVEFORMATEX` / `WAVEFORMATEXTENSIBLE`), `strn` |
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| Index | OpenDML `indx` super index → `ix##` standard indexes (field indexes too), else `idx1` (offsets relative to `movi` or absolute), else a scan of the `movi` lists |
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| Large files | `RIFF AVIX` extensions: through the OpenDML index, or scanned after `idx1`, which only covers the first RIFF |
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| Key frames | from the index; a scan marks every chunk and says so (`keyframes_known`) |
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| Damage | sizes clamped to the file (a cut-off recording opens with what is there), `rec ` lists nested at most 3 deep, tables bounded by what the file could hold |
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`filmcraft-codecs` maps the streams onto decoders (`AviSource`): Motion JPEG, H.264, HEVC and
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uncompressed RGB / YUV video; PCM, MP3, MP2 and AC-3 audio.
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## Tests
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`cargo test -p filmcraft-avi`: hand-built files for every index path (`idx1` relative and absolute,
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`rec ` lists, OpenDML standard indexes, a scan), truncation, and every single-byte mutation and
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truncation of them (never a panic). `tests/ffmpeg_oracle.rs` checks ffmpeg-made files (Motion JPEG,
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H.264 with B-frames, BGR24, YUY2; PCM and MP3) against ffprobe; the ignored `opendml_file_past_1_gb`
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checks a 1.16 GB OpenDML file with `AVIX` extensions.
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